Effect of Time-strengthening Static Friction on Earthquake Recurrence

Jeen-Hwa Wang

doi:10.4401/ag-8382

Abstract

he effect of time-strengthening static friction on earthquake recurrence is numerically studied based on the normalized equation of motion of a one-body spring-slider model with thermal-pressurized slip-weakening friction having the characteristic distance, Uc, which is in terms of static friction coefficient, 𝜇. Considering the time-strengthening static friction coefficient, 𝜇(𝑡) = 𝜇+𝐵×𝑙𝑜𝑔(𝑡), we assume Uc=Uco/(1+𝐵×𝑙𝑜𝑔(𝑡)). Simulation results exhibit that TR, 𝜏D, D, and Vm, which represent the recurrence time of two events, the duration time of slip of an event, the final slip of an event, and the peak value of particle velocity of an event, respectively, are all similar for five values of Uco when B<0.01 and clearly different when B≥0.01. In general, Vm, D, and TR increase with B; and 𝜏D slightly decreases with increasing B and increases with Uco. An increase in D is particularly remarkable when Uco>0.3. The earthquake recurrence is almost periodic for small Uco; while the degree of periodicity decreases when either Uco or B increases. Either the time-predictable model or the slip-predictable model can approximately interpret the simulated earthquake recurrences with small Uco and small B, yet not for those with large Uco and large B. Simulation results exhibit that time-strengthening static friction produce an opposite effect on earthquake recurrence from the time-widening slip zone.

Highlights

Earthquake recurrence, which represents the repetitive occurrences of events on a fault during a long time period, is an important factor in assessing seismic hazards
The main parameters are the normalized characteristic displacement, Uc, of the friction law and the normalized damping coefficient, η, which is used to represent viscosity. His simulation results show that TR increases with decreasing Uc or increasing η; D and τD decrease with increasing η; and τD increases with Uc
He assumed that CV and Do are minor in affecting Uc; while time-dependent ρf and Λ are important in influencing Uc and on earthquake recurrence

Summary

Introduction

Earthquake recurrence, which represents the repetitive occurrences of events on a fault during a long time period, is an important factor in assessing seismic hazards. The main parameters are the normalized characteristic displacement, Uc, of the friction law and the normalized damping coefficient, η, which is used to represent viscosity His simulation results show that TR increases with decreasing Uc or increasing η; D and τD decrease with increasing η; and τD increases with Uc. The time- and slip-predictable model can describe the temporal variation in cumulative slip. Uc is a function of h and depends on cumulated slip, ∑U, with an increasing rate of C His simulation results reveal that the wear process influences the recurrence of events and the effect increases with C when C>0.0001. We will investigate the effect on earthquake recurrence caused by time-strengthening static friction coefficient based on a one-body spring-slider model. From numerical simulations based on this model in the presence of thermal-pressurized friction and viscosity, we can obtain significant information of frictional and viscous effects on earthquake recurrence along a single fault

One-body model and numerical methodology

Simulation results

Discussion

Summary